Binding agent for photographic emulsions and method of preparing same



Patented Feb. 16, 1937 PATENT OFFICE nmnme AGENT ronrno'roemmc EMULSIONS AND PARIN G SAME llenno Bochskanill, Hamburg, Germany,

by mesne assignments, to International Development Company, Wil

METHOD or ran- #8 8 Patents mington, DeL, a

corporation of Delaware No Drawing. Application June 29, 1933, Serial No.- 6'I 8,319. In Germany I llclaims.

This invention relates to the production of photographic emulsions.

One object of the invention is to cheapen the manufacture of these emulsions, whilst a further objectis to increase the adhesive powers thereof and'thelr resistance to temperature.

- As well known, the usual gelatine emulsions adhere to the backing of the film, particularly if the-latteris composed of nitro-cellulose, in very deficient manner, so that-it is necessary to furnish the backing with a preparation which ensures connection between the same and the coating of emulsion. 0n the other hand gelatine emulsions, regardless of the backing to which the same are applied. whether this be glass, film or paper, possess the disadvantage that they are extremely sensitive to increases in temperature, forwhich reason a hardening of the coating is usually performed, particularly in the case of so-called tropical emulsions. This hardening, however, which amounts to a tanning of the gelatine colloid also possesses the disadvantage that the coating is not readily pervious to liquid,'thus impairing the requisite treatment in the baths.

; According to the invention, these disadvantages are overcome by employing as a photographic emulsion,- or emulsion for similar purposes, a mixture of film-forming, pourable, disintegrated starch and gelatine with a hardening agent, such as chrome-alum. .to which there are naturally added when the emulsion is' to be used for photographic purposes and, before the emulsion is poured, the constituents necessary, for forming the light-sensitive salts. 1

A preferred method of producing the binding agent consists in at first boiling the disintegrated illm forming starch with water, admixing the product when still hotwith the hardening agent, for, example chrome-alum, and then adding to the somewhat cooled mass the gelatine solution. Ithasalreadybeenproposedtoaddtophotographic emulsions starch in dry, unsoaked or also in paste-like condition.- This, however, did not refer to a'dislntegrated film-forming starch, whilst the same is also intended for a wholly different purpose, via an opalization of theemulsion. In this connection additions of starch are sufiicient in such a small quantity that the-ability to pour the emulsion is not appreciably aifected. In con- .tradistinction thereto it is the object of the invention to replace the gelatine to alarge extent in photographic emulsions by a starch which has been disintegrated to such'exient as to impart film-forming properties to the same. It is a suriiprlslngfeatiuethatthe ability'to pourthe emula January 28, 1933 (Cl. 95-'i) sion is not ailected'even if large quantities of this starch are employed with small amounts of gelstine.

Emmple.--Washed corn starch in approximately 35% solution is disintegrated for approxi- 5 mately 12-15 hours under continuous agitation with a watery alkaline sodium hypochlorite solution at ordinary temperature, and then washed and dried. The dilute character of the sodium hypochlorite solution prevents change in the starch molecules to a point where the starch. product is readily soluble in water. '7 grammes of this disintegrated film-forming starch are heated with approximately 50-55 ccm. distilled water in a water bath, with suitable agitation, 15 the same serving to produce 100 grammes photographic emulsion when ready for pouring. when a temperature of 75 C. has been reached there are added 8 com. chrome-alum solution (1:50), previously admixed with ammonia, until a weak clouding takes place.

Heating is now additionally performed up to 80-85. In the meantime the gelatine (ordinary commercial emulsion .gelatine) is prepared for soaking,- -1 gramme gelatine being soaked in 30 grammes distilled water. In the water there is dissolved at the same time the necessary amount of bromide of potassium. After soaking the gelatineis dissolved by heating to approximately 60 C. This gelatine solutionv is stirred well into the starch solution, which also'has a temperature of approximately After the two solutions have been mixed together there is added the requisite amount of silver nitrate, dissolved in 10 ccm.

water. The emulsion having been prepared in 5 the described fashion, the same is cooled, and pouring takes place at approximately 2'1-28 C. Before pouring, the soluble salts, if desired, may be removed in the mannerJmown per se by coagulating the emulsion and washing the same in water, and then melting the same again. by heat- It. is obvious that all operations after the formation of ,the light-sensitve silver bromide require to be performed in a darkroom. 4

In the above example the ratio between the airdried starch and the air-dried gelatine amounts,

in weight, to 1:7. It will be obvious, however, i that other proportions may be employed dependent on the requirements placed on the emul- 5 sion. Thus, for example, the coagulation may be I greatly increased by increasing the proportion of gelatine. In this case, however, the otherconstitutents, and. particularly the proportion of the hardeningagent, must be adapted accordingly.

The proportion or g'elatine, however, is important- If the gelatine were omitted entirely, the mass would lose its solidifying pOwers and accordingly also its ability of being poured, and

gelatin solution, and finally a light sensitive salt.

aomm

7. Method of producing a pourable photographlc' emulsion which consists in heating a film-forming, substantially cold water insoluble, disintegration product of starch and water, addmixture.

' BE NNO BOCHSKANDL.

1 would not be suitable for the usual manipulations ing to the mixture while hot chrome alum, and performed in the preparation of the emulsion, then adding to the somewhat cooled mass a gelviz., the washing and coagulation, melting, and atin solution, and finally a light-sensitive salt. bearing with the immersed roller and plate 8. Method of producing a pourable emulsion pourer, for which purpose, as well known, a for photographic and like uses which comprises:

distinct solidifying-point is absolutely essential. producing a film-forming starch product, sub- 1 Adjustment of the solidifying point to a certain stantially insoluble in cold water, by disintegratpouring temperature may be performed by varying corn starch by treatment for twelve to fifteen ing the proportions of the substances. hours at ordinary room temperature with a di- It will be understood that no restriction is lute alkaline hypochlorite; treating the disin- 1 made to the particular example quoted, and that tegrated starch with a. hardening agent and in- 1 various modifications are quite possible within corporating gelatin with the material in substanthe meaning of the above description and the tially the proportion of 1 part by weight of gelaannexed claims without departing from the spirit tin to 7 of starch. of the invention. 9. Method of producing a pourable emulsion What I claim as new and desire to secure by for photographic and like uses which comprises: 20 Letters Patent is: producing a film-forming starch product, sub- 1. A coherent insoluble transparent substance stantially insoluble in cold water, by disintegratconsisting of a chromated compound of gelatin ing the starch in water with a dilute alkaline hyand film-forming, substantially cold water insolpochlorite at ordinary room temperature; washuble, disintegrated starch. ing the disintegrated starch in water to a tem- 25 2. A photographic film consisting of a chroventure of about C; adding chrome alum mated compound of film-forming, substantially to the material and increasing the temperature cold water insoluble, disintegrated starch, and of the same to about 80. to 85 C.; incorporating gelatin in which a light sensitive salt is incorgelatin with the material; and cooling and pourporated, ing the mixture. 30

3. Pourable emulsion for photographic nd lik 10. A cold water insoluble transparent photopurposes comprising an aqueous mixture of gelr phic film c is ing of a chrom mp n atin and a film-forming, substantially cold water of filmo min di n e starch d gelatin insoluble, product, of tarch, together ith a in which a light sensitive salt is incorporated, to-

hard ni agent, gether with a hardening agent, the proportion 4. Pourable emulsion for photographic and like between the gelatin and the disintegrated starch purposes comprising an aqueous mixture of gela,-' being substanti ly one p rt by Weight of el tin and a film-forming, substantially cold water tin to seven of starch. insoluble, disintegration product of starch, to- Method Of Producing a D a e uls on 4.0- gether with chrome alum for photographic and like uses which comprises: 40

5. Method of producing a pourable emulsion producing a film-forming starch product by disfor photographic and like uses which comprises: ig i gg gfig fr gg gl g' gfi z gg gggg gzgs film-forming starch i subwith a watery alkaline sodium hypochlorite soluany insoluble in coldwater' by dismtegmt' tion washing the disintegrated starch and dry- 4' r J ,ing starch by treatment with a dflute alkaline mg the same adding water to the dry starch and hypochlorite'; treating the distintegrated starch heating, h agitation to approximatly with hardening agent; and mmmmtm gelacentigrade; adding a chrome-alum solution to tin with the materialthe material until a weak alkaline reaction re- Method of Producing poumble Photo sults, at the same time increasing the tempera- 50 graphic emulsmn which in heating ture to about- 80 to 85 centigrade; incorporatfilm-forming, substantially cold water insoluble, m gelatin with the material in the proportion product! of Starch in Water, adding of approximately one gelatin to to th mixture w leh t a ha d nin a nt and seven of starch; and cooling and pouring the then adding to the somewhat cooled mass a CERTIFICATE OF CORRECTION.

Patent No. 2,070,575. a February 16, 193

BENNO BOCHSKANDL It is hereby certified that. error appears in the printed specification of the above numbered patent requiring correction as follows! Pag 2, first column, line 34, claim 3, before the word "product" insert disintegrated; and that the said Letters Patent should be read with this correction there in that the same may conform to the record of the case in the Patent Office.

Signed and sealed thisfSOth day of March, A. D. 1937.

Henry Van Arsdale (seal) Acting Commissioner of Patents. 

